Derangement of regulation of protein degradation in transforming fibroblasts

Abstract
Changes in endogenous protein degradation of stable proteins with growth state have been observed in a number of normal cell lines. Increases in degradation of between 15% and 40% occurred in 10 cell lines at confluence. No such regulation of proteolysis was observed in 4 cell lines [2 lines of mouse fibroblast 3T3 cells, 3T6 cells and Chinese hamster ovary, CHO-K1 cells] which were clonogenic in soft agar. This derangement of regulation apparently coincides with the transformation of cells. Regulation disappears in spontaneously transforming fibroblasts and is decreased by the tumor promoter 12-O-tetradecanoyl-phorbol-13-acetate. Regulation reappeared in a growth control revertant of a transformed (3T3) line. [Other cell lines studied include human fibroblasts, baby hamster kidney BHK21c13 cells, African green monkey kidney BSC-1 cells and human embryonic lung MRC-5 cells.].